1. Field of the Invention
This invention relates generally to exercise machines, and is particularly concerned with a leg press exercise machine.
2. Related Art
The most widely performed free weight exercise for the lower body is the barbell squat. It is a compound movement exercise, requiring the movement of multiple joints, specifically the knee and hip, and multiple body parts, specifically the upper and lower legs. To perform the exercise, an exerciser stands erect, places a weighted bar across their shoulders and bends at the knees, squatting downward until the upper thighs are parallel to the floor. During the exercise, it is important to maintain a certain body alignment. The head should be upright, eyes looking forward; feet should be approximately shoulder width apart; the back should remain straight; and the knees should point forward and be positioned over the toes in the squat or low position of the exercise movement. Balance is a critical part of the exercise as unwanted front to back or side to side movement could create instability and disrupt alignment, which in turn could result in injury.
The leg press machine was designed to provide a safer squatting exercise by eliminating the problem of balance and stability. These machines reverse the start and finish positions by placing the user in the compressed or squat position at the start of the exercise and in the extended position with their legs straight at the finish. One version of a leg press consists of a stationary user support with a movable exercise arm. The user either sits upright or reclines in a prone or semi-prone position, places their feet upon a footplate attached to the exercise arm and pushes the arm forward. A variation of this design has the footplate stationary and the user support movable. In both these scenarios, the movement of the user support or exercise arm could be arcuate or linear.
While the movement is similar to a free weight squat, these leg press machines do not provide the same body alignment or positioning because they do not adjust the position of the user to the position of the footplate during the exercise movement. During a free weight squat, the body is constantly making minor adjustments to keep the feet, knees and back in proper alignment. This adjustment does not take place just at the beginning or end of the exercise; it happens continuously throughout the entire movement and, although balancing a bar on ones shoulders while bending at the knees can be tricky, it forces core stabilizing muscles in the abdomen and low back to be involved. Leg press machines that utilize a pivoting exercise arm can cause an exaggerated arcing movement during the exercise. An unnatural straight line movement is produced in leg press machines that utilize a linear movement exercise arm. Neither of these exercise machines provides body positioning equivalent to that of a free weight, barbell squat.